The study of the structure of the 7S nerve growth factor (NGF) protein and its constituent subunits and of their role in neuronal development will be continued. The effect of the limited and specific proteolytic cleavages and the conformation dissociation equilibrium and biological activity of the Beta NGF subunit will be examined. Both alpha and gamma subunits are heterogeneous and its basis will be sought by determining the peptide chain compositions before and after proteolysis induced by enzymes in the submaxillary gland. Attempts to determine the physiological role of the 7S complex will be made by studying its assembly and its biological activities before and after cross-linking with dimethylsuberimidate and other reagents. The putative $ precursor to Beta NGF will be sought by specific precipitation of labelled extracts of submaxillary gland with antibody to Beta NGF. Continued characterization of the NGF receptors will involve comparisons of different methods of iodination and of different tissue sources of receptors and the effects of the monomer, dimer equilibrium on specific binding. The cellular localization of the receptor and of its fate during development will be sought using in vitro cultures of dissociated sympathetic and sensory ganglia.